Here we show that oxide heteroepitaxy could provide an attractive solution in virtual of the layer-controlled synthesis of quantum well structures. We demonstrated this approach through an artificial superlattice (SL) where we combined monolayer and bilayer \(J_{\rm eff} = 1/2\)  square lattices by stacking one- and two-unit-cell thick SrIrO\(_3\)  slabs with SrTiO\(_3\)  spacing layers in-between [Fig.1 (a)]. Such a layered superstructure is an ideal prototype because a dimensionality-controlled spin-flop transition between monolayer and bilayer iridates have been well established [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}. Specifically, while both of them have the \(J_{\rm eff} = 1/2\)  antiferromagnetic (AFM) insulating state cooperatively stabilized by the strong spin-orbit coupling and the electronic correlation [1]}, [12]}, [4]}, [14]}, [15]}, [16]}, [17]}, the XY-anisotropy of the monolayer is turned into the strong \(c\) -axis Ising anisotropy in the bilayer due to the interlayer coupling [18]}, [19]}, [20]}, [21]}, [22]} [Fig.1 (a)]. Despite the debate on the origin of the interlayer coupling and its role in the spin-flop transition [19]}, [24]}, [25]}, [26]}, [27]}, [28]}, bringing the monolayer and the bilayer together in one structure would create an intriguing scenario to explore the proximity effect of two states with orthogonal anisotropy. The enforced competition or cooperation between monolayer and bilayer makes such a hybrid structure a good candidate to achieve new emergent states [29]}, [30]}, [31]}, [22]}, [33]}, [34]}.
